Reverse plating timer



May 20, 1952 E. c. HARTWIG REVERSE PLATING TIMER Filed Nov. 2, I948ATTORN EY INVENTOR Edward C. Hcr'rwig.

Patented May 20, 1952 REVERSE PLATING TIMER Edward C. Hartwig,Tonawanda, N. Y., assignor to Westinghouse Electric Corporation, EastPittsburgh, Pa., a corporation of Pennsylvania Application November 2,1948, Serial No. 57,997

Claims.

My invention relates to electronic timers and particularly to timersuseful in reverse electroplating operations.

A novel electroplating method has been developed in which platingcurrent of one polarity is applied for a period of 2 to 40 seconds todeposit a microscopic increment of metal and then the current isreversed for a period of from /2 to 5 seconds, respectively, to remove aportion of the previously plated increment. This method and theresultant advantages are explained more fully in the copendingapplication, Serial No. 610,107, filed August 10, 1945, now Patent No.2,451,341, dated October 12, 1948. and assigned to Westinghouse ElectricCorporation. An automatic timer is required to provide accurate timingintervals for this purpose.

In some operations reverse plating processes have been carried out withthe use of synchronous motor timers. Such timers have severaldisadvantages some of which harm the effectiveness of the electroplatingprocess and others of which render the process slower and moreexpensive. Tests made with one synchronous motor timer indicate thattiming errors are often of the magnitude of .02 to .04 second and remainsubstantially constant when the length of the timing interval ischanged. If the error remains Within the same range when /2 second isthe time interval such a synchronous motor will provide timing oftenhaving an error of 4% to 8%. Such an error is likely to change greatlythe characteristics of a plating job.

Further disadvantages are found in the difficulty incurred in changingthe timing interval measured by synchronous motor timers. It is thecustom in suing synchronous motor timers of which I am aware to changethe timing interval by changing the cam mechanism which actuates theswitches. If a manufacturing process is such that several different timeintervals must be measured by the same at different times by the sametimer, the labor involved in changing the cams used on the timers willbecome burdensome.

It is accordingly an object of my invention to provide a reverse platingsystem in the operation of which the duration of the currents ofopposite polarity shall be accurately timed.

It is also an object of my invention to provide a novel electronic timerfor use with reverse electroplating apparatus.

It is a further object of my invention to provide an electronic timerwhich will pass current of one polarity through a load for apredetermined time interval and pass current of the other polarity foran independently controlled interval.

In accordance with my invention, a pair of electric valves having atleast three electrodes are connected across a source. A timing capacitorconnected to the control electrode and cathode of the first valve ischarged to a potential sufficient to block the conductivity of thatvalve. When the second valve becomes conductive, it actuates a relaywhich controls the flow of electroplating current and shunts chargingcurrent by the timing capacitor. After a predetermined time interval,the capacitor is discharged through a resistor sufiiciently to decreasethe biasing voltage of the first valve and allow it to becomeconductive. Current flowing through the first valve charges a secondtiming capacitor, which is connected to the control electrode andcathode of the second valve, to such a potential that it causes thesecond valve to become non-conductive. When the second valve becomesnon-conductive, it reverses the electroplating current and interruptsthe anode-cathode circuit of the first valve causing the first valve tobecome non-conductive. The timing capacitor connected to the controlelectrode of the second valve then discharges through a bleeder resistorsufficiently to allow the second valve again to become conductive, andthe cycle of operation is repeated.

The features of my invention which I consider to be novel are set forthwith more particularity in the appended claims. The invention itself,however, together with additional objects and advantages thereof, may bebetter understood from the following description of a specificembodiment thereof when read in connection with the accompanying drawingin which:

Figure 1 is a circuit diagram of a control system embodying myinvention, and

Fig. 2 shows a modification of a control system according to myinvention.

As shown in Fig. 1, one terminal 3 of the secondary 4 of a powertransformer 5 is connected through a start switch I, an electric valve9, a resistor II, the operating coil 13 of a relay [5 to the otherterminal I! of the transformer secondary 4. An anti-chattering condenserI9 is connected across the operating coil l3 of the first relay I5, Asecond circuit may be traced from one terminal 3 of the transformersecondary 4 through a variable resistor 2| and first timing capacitor 23in parallel, a second resistor 25, the anode 21 and cathode 29 of thesecond electric valve 3|, and the normally open contacts 33 of the relay15 to the other terminal ll of the secondary winding 4. The control grid35 of the first valve 9 is connected through a grid resistor 37 to thefirst timing capacitor 23. The control grid 39 of the second Valve 3i isconnected through a grid resistor 4| and a second timing capacitor 43and second variable resistor 45 connected in parallel, to the lowerterminal I! of the transformer secondary 4. A charging resistor 46 isconnected between the upper terminal 3of the transformer secondary 4 andthe cathode 29 of the second valve 3 A circuit can be traced from oneterminal of the primary winding 41 of the transformer 5 through arectifier 49, the actuating coils 5| of a second relay 53 and the relaycontacts 55 to the other terminal of the primary 4? of the transformer5. A condenser 51 is connected across the operating coils of the secondrelay to smooth the rippling current through the relay 53.

The electroplating circuit may be traced from the positive terminal of asource of direct current illustrated as a battery 59 through thenormally closed contacts 6|, the plating electrodes 53 and the normallyclosed contacts 65 to the negative terminal of the source.

Operation of the circuit is initiated by closure of the starting switch1 which impresses the line potential across the first valve 9. Thecontrol electrode 35 of the first valve 9 is at a firing potential,since the first timing capacitor 23 is now maintained in an unchargedcondition by its bleeder resistor 2|. The first valve 9 now becomesconductive actuating the first relay |5 and thereby closing the normallyopen contacts 33 in the cathode circuit or" the second valve 3|.

Prior to closure of these contacts 33, the second timing capacitor 43has been charged through the charging resistor 45, the cathode 29 andthe control grid 39 of the second valve 3| and the grid resistor 4|. Theterminal of the second timing capacitor 43 connected to the grid 39 isnegative with respect to the terminal connected to the cathode 29. Whenthe relay contacts 33 are closed, the control grid 39 of the secondvalve 3| is negative with respect to the cathode 29 and this valve 3|cannot become conductive. The charging resistor 46 i now connecteddirectly across the transformer secondary 4 and no longer passescharging current to the second timing condenser 43. The second timingcondenser 43 now discharges through its variable bleeder resistor 45,and the grid 39 of the second valve 3| become less negative until thesecond valve 3| becomes conductive. When this valve 3| becomesconductive, it passes current through the resistor to the first timingcapacitor 23 charging it so that its left-hand terminal becomes negativewith respect to its right-hand terminal. Valve 9 is then renderednon-conductive.

The first valve remains non-conductive, deactivating the first relay l5and opening the cathode circuit of the second valve 3|. The second valve3| becomes non-conductive allowing the first control capacitor 23 todischarge through its bleeder resistor 2|, until the grid of the firstvalve 9 is at a potential above the critical firing potential and thefirst valve 9 becomes conductive. The cycle is then repeated.

At the beginning of operation the normally closed contacts 55 of thefirst relay closes a circuit through the lower operating coil 5| of thesecond relay 53. This hold closed the normally closed contacts 6| and 65of the electro-plating circuit and the upper plating electrode ispositive. When the first valve 9 is conductive, it actuates the coil l3of the first relay l5 closing the normally open contacts 56 and openingthe normally closed contacts 6| and 65 of the electroplating secondrelay 53 is actuated and the lower coil 5| is released. The second relaythen opens the normally closed contacts 65 and 6| and closes thenormally open contacts 67 in the electroplating circuit, and the lowerplating electrode becomes positive.

In this circuit the first relay |5 controls the operation of the secondrelay 53, which in turn determines the polarity of the platingelectrodes 63. If it is desired, the first valve 9 can have a currentrating which will allow it to actuate a larger relay than the one I havedescribed. If such a valve is chosen, the first relay I5 can beconnected so as to reverse the electroplating current directly and thesecond relay 53 can be eliminated.

Fig. 2 shows a modification of certain portions of Fig. 1. The changesrelate to control of the grid of the second tube 3|. The relay I5 isconnected between the grid timing circuit and one terminal ll of thesecondary 4 of the supply transformer 5. A mid-tap 69 on the supplytransformer 5 is connected to the cathode 29 of the second tube 3|. Aresistor 1| is connected between one terminal ll of the supplytransformer 5 and the contact 13 of the relay IS. A voltage regulatortube 15 is connected between the mid-tap E9 of the supply transformer 5and the contact 13 of the relay I5. A capacitor 43 is connected betweenthe grid 39 of the second tube 3| and contact 13 of the relay [5. Avariable resistor is connected across the capacitor 43. The cathode 29of the second tube 3| is connected through the actuating coil I3 of therelay l5 to the anode of the first tube 9. The cathode of the first tube9 is connected through the start switch I through one terminal 3 of thesupply transformer 5.

As was the case with the modification shown in Fig. 1, operation of thecircuit is initiated by closure of the starting switch i which connectsthe first valve 9 across a portion of the secondary 4 of the supplytransformer 5. The first valve 9 becomes immediately conductiveactuating the relay |5 to open the contacts 13.

Prior to closure of the starting switch I, the capacitor 43 has beencharged by a grid current flowing from one terminal I! of the supplytransformer secondary 4 through the resistor H, the close contact 13,the capacitor 43, grid 33, and the cathode 29 of the second tube 3| tothe center tap 69 of the supply transformer 5. The peaks of the voltagewave supplied by the transformer 5 are made uniform by the action ofvoltage regulated tube 15. The capacitor 43 is thus charged to aplurality which will cause it to bias the grid 39 of the second valve tosuch a potential as to cause the second valve 3! to remain unconductive.

When the contacts 13 are opened as a result of current flow through thefirst valve 9 and the actuation coil [3, the charging circuit of thecapacitor 43 is opened and the capacitor 43 begins to discharge throughthe resistance 45. After a pre-set time interval the second valve 3|becomes conductive and begins to charge the capacitor 23. After thecapacitor 23 has been charged sufficiently, the voltage of the grid 35of the first valve 9 is lowered so that the first valve 9 becomesnonconductive. The contacts 13 reclose and the capacitor 43 again beginsto charge in such a way as to bias the grid 39 of the second valve 3| tonon-conductivity. The second valve 3| becomes non-conductive and thetiming capacitor 23 discharges through its leader resistor 2| raisingthe potential of the grid 35 of the first valve 9 until the first valveagain becomes conductive. This sequence of operations continues thusproviding timed opening and reclosing intervals for th relay |5. Therelay I5 is connected to the electroplating circuit in the manner shownin Fig. 1.

Other elements of this circuit are the same as those shown in Fig. 1.

While I have shown and described a specific embodiment of my invention,I am aware that many other modifications thereof may be made withoutdeparting from the spirit of the invention. I do not intend therefore tolimit my invention to the specific embodiment disclosed.

I claim as my invention:

1. In combination, a first electron discharge device having an anode, acathode, and a control electrode and adapted to be connected to a sourceof current, an energy storage device adapted to be connected betweensaid control electrode and one terminal of said source, a di rectcurrent path from the other terminal of said source to said energystorage device, a second energy storage device connected between oneterminal of said source and one electrode of said first electrondischarge device, a second el ctron discharge device having an anode, acathode, and a control electrode and adapted to be connected in circuitwith said source, connections between said second energy storage deviceand the control electrode of said second electron discharge device, arelay in circuit with said second electron discharge device and havingcontactors, connections between said contactors and said first energystorage device such that said contactors control the charging of saidfirst energy storage device, and connections between said contactors andsaid first electron discharge device such that said contactors controlthe continuity of the anode-cathode circuit of said first electrondischarge device.

2. In combination, a first electron discharge device having an anode, acathode, and a control electrode and adapted to be connected to a source01 current, a capacitor adapted to be connected between said controlelectrode and one terminal of said source, a direct current path fromthe other terminal of said source to said capacitor, 2, second capacitorconnected between one terminal of said source and one electrode of saidfirst electron discharge device, a second electron discharge devicehaving an anode, a cathode, and a control electrode and adapted to beconnected in circuit with said source, connections between said secondcapacitor and the control electrode of said second electron dischargedevice, a relay in circuit with said second electron discharge deviceand having contactors, connections between said contactors and saidfirst energy storage device such that said contactors control thecharging of said first energy storage device, and connections betweensaid contactors and said first electron discharge device such that saidcontactors control the continuity of the anode-cathode circuit of saidfirst electron discharge device.

3. In combination, a first electron discharge device having an anode, acathode, and a control electrode and adapted to be connected to a sourceof current, an energy storage device adapted to be connected betweensaid control electrode and one terminal of said source, connectionsincluding a high impedance between the anode and the cathode of saidfirst electron discharge device, a second energy storage device adaptedto be connected between one terminal of said source and one electrode ofsaid first electron discharge device, a second electron dischargedevice, having an anode, a cathode, and a control electrode and adaptedto be connected in circuit with said source, connections between saidsecond energy storage device and the control electrode of said secondelectron discharge device, a relay in circuit with said second electrondischarge device and having contactors, connections between saidcontactors and said first energy storage device such that saidcontactors control the charging of said first energy storage device, andconnections between said contactors and said first electron dischargedevice such that said contactors control the continuity of theanode-cathode circuit of said first electron discharge device.

4. In combination, a first electron discharge devic having an anode, acathode, and a control electrode and adapted to be connected .to asource of current, an energy storage device adapted to be connectedbetween said control electrode and one terminal of said source, a directcurrent path having a high impedance adapted to be connected between theother terminal of said source and said energy storage device, a secondenergy storage device adapted to be connected between one terminal ofsaid source and one electrode of said first electron discharge device, asecond electron discharge device having an anode, a cathode, and acontrol electrode and adapted to be connected in circuit with saidsource, connections between said second energy storage device and thecontrol electrode of said second electron discharge device, a relay incircuit with said second electron discharge device and havingcontactors, connections between said contactors and said first energystorage device such that said contactors control the charging of saidfirst energy storage device, and connections between said contactors andsaid first electron discharge device such that said contactors controlthe continuity of the anode-cathode circuit of said first electrondischarge device.

5. A timer for controlling current flow in a first circuit, a secondcircuit comprising a first electric valve having an anode, a cathode,and a control electrode and connected across a source of alternatingcurrent, a capacitor connected in a resistive circuit between saidcontrol electrode and the cathode, a second electric valve having ananode, a cathode, and a control electrode and being connected betweenone terminal of said source and a terminal of said capacitor, acapacitor connected in a resistive circuit between the cathode of saidsecond electric valve and the control electrode of said second valve, ahigh impedance path connected between one terminal of said source andthe cathode of said second electric valve, and a relay havingcontactors, connections between said contactors and said first energystorage device such that said contactors control the charging of saidfirst energy storage device, and connections between said contactors andsaid first electron discharge device such that said contactors controlthe continuity of the anode-cathode circuit of said first electrondischarge device.

EDWARD C. HARTWIG.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,534,709 Holt Apr. 21, 19252,053,143 Frederick Sept. 1, 1936 2,306,237 Wolfner Dec. 22, 19422,313,943 Jones Mar. 16, 1943 2,421,835 Durant June 10, 1947 2,442,238Haung May 25, 1948 2,451,341 Jernstedt Oct. 12, 1948 2,463,318 Schneideret a1 Mar. 1, 1949

